Universiteit Leiden

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Research project

TRIPS: Thrips Reduction In Production Systems

Increasing above- and belowground biodiversity in arable leek cultivation to stimulate pest control by natural enemies.

2024 - 2029
Eelco Hoogwout

Research questions

  • How can biodiversity in the production system be increased and integrated into the production system and what are the effects on the wider environment?
  • What are the effects of increased biodiversity on resilience against biotic stress?
  • How can integration of biological pest control agents reduce the harmful effects of phytophages?
  • Which governance aspects are needed to boost and facilitate the large scale application of systems that increase biodiversity?
  • How much societal support is available for stimulating biodiversity in primary production systems and how can this be increased?


Leek is an important crop particularly in Limburg and Noord-Brabant and thrips is the major pest in this cultivation. Thrips is conventionally controlled with pesticides with clear negative effects on the environment, biodiversity and the health of both growers and consumers. With a multidisciplinary consortium of agronomists, ecologists, economists, governance scholars, growers, stakeholders and governmental organizations we aim to create a widely supported, sustainable leek cultivation system which is less dependent on pesticides, entails more biodiversity in the crop and wider environment, and with improved soil health. We propose to examine how the introduction of flowering banker-plants, aboveground natural enemies of thrips, and belowground organic additions will control thrips and stimulate soil biodiversity and belowground control of thrips. In the new system, thrips populations will be initially suppressed by introduced predators, but later in the season by locally present natural enemies that have been promoted by the introduced banker-plants and alternative resources. The safe production of healthy food in a nature-positive way is a significant societal challenge. In this project, in collaboration with growers, suppliers, other experts and policy makers, we aim to identify and overcome agronomic, legal, social and practical barriers to adopt this new system and make it economically viable and attractive. We will make use of existing long-term relationships with actors of the entire leek cultivation chain, and work with them in all phases of the programme; during project development, in the test and experimental phase, and in the transition towards the new system.

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